1. Field of the Invention
This invention generally relates to the field of communications. More particularly, the present invention relates to a communications processor that improves the quality of potentially degraded data transmission signals operating at high transmission rates.
2. Description of Related Art
Advances in computer capabilities as well as the unprecedented growth of Internet-related transactions have placed great demands on conventional communication infrastructures to convey information to subscribers at higher transmission rates with increased reliability and levels of service. Although conventional infrastructures communicate at higher transmission rates between networked hubs, such as DS-3 (e.g., or 45 Mbps) and OC-3 (e.g., or 155 Mbps), they are generally limited in their ability to accommodate such ample bandwidths between the hubs and subscribers. Such limitations arise from the infrastructures"" inability to compensate for degradations encountered over conventional transmission media spanning distances of up to 18,000 ft. between the hubs and subscribers.
Consider, for example, how common carriers provide connectivity to subscribers. Typically, carrier hubs or central offices connect to subscribers via subscriber loop circuits. Subscriber loop circuits generally comprise 2-wire transmission paths (i.e., unshielded twister pairsxe2x80x94UTP), which support direct current signals, low frequency ( less than xcx9c200 Hz) analog signals, and voice band signals (xcx9c200 Hz-xcx9c3.4 KHz). This range of frequencies limits the transmission rate at which digitally-encoded signals can be conveyed by the 2-wire transmission paths. Moreover, the longer the distances traversed by the signals on these 2-wire transmission paths, the more severe the degradation of the signals, thereby relegating communications to lower transmission rates. This assumes, of course, that the signals are pristine at inception; degraded signals may be subject to even lesser transmission rates to meet acceptable transmission error rates.
Recent efforts have sought to increase the digital transmission rates conveyed by the 2-wire transmission paths. Such efforts include the development of asymmetric digital subscriber lines (ADSLs). ADSLs implement a combination of channelization (e.g., discrete multi-tone DMT), coding (e.g., constellation/trellis encoding), and framing (e.g., super-framing) techniques to achieve upstream digital rates between 64-640 Kbps and download digital rates between 500 Kbps-7 Mbps. The ability to effectively attain these transmission rates, however, is very dependent on the distance the transmission must travel. Clearly, the longer the distance, the greater the distortion of the data at these transmission rates. Furthermore, ADSLs are sensitive to line-quality and line configurations. As a result, the higher transmission speeds are only available to subscribers having xe2x80x9cclean linesxe2x80x9d (i.e., no abrupt changes in line impedance due to wire gauge changes, bridge taps, coils, etc.) that are within very specific distances from the central office (e.g., 8,000-10,000 ft.).
Other efforts include performing line-conditioning to increase the line-quality of a local loop in the hopes of accommodating higher transmission rates. Such conditioning may include removing wire gauge changes, bridge taps, and coils, and other abnormalities. However, while such conditioning may provide moderate improvement in transmission speeds, it is time and labor intensive and line specific. In addition, much like ADSLs, improvements in transmission rates are acutely dependent on distance.
As a result, there is a need for an apparatus capable of receiving degraded data transmission signals operating at high transmission rates and reconstituting the signals to improve their signal quality in a manner that allows the signals to be transmitted over longer distances than is otherwise possible using conventional methods.
Consistent with the principles of the present invention, as embodied and broadly described herein, exemplary embodiments may include an apparatus or method (or one or more subcomponents of such apparatus or method) for receiving a data transmission signal operating at a predetermined transmission rate and generating an improved data transmission signal. Such an apparatus may include a decoding mechanism coupled to the data transmission signal and an external clock reference signal having a predetermined clock rate matching the predetermined transmission rate of the data transmission signal. The decoding mechanism is configured to compensate for amplitude and phase distortions of the data transmission signal, to split the corrected data signal into component data signals, to generate a data clock reference signal based on the data transmission signal and the external clock reference signal and to convert the component data signals into digital component data signals synchronized to the data clock reference signal. The apparatus further includes an encoding mechanism coupled to the decoding mechanism. The encoding mechanism is configured to receive the digital component data signals and the data clock reference signal and to convert the digital component data signals into analog component data signals. The apparatus then selectively outputs at least one of the analog component data signals as the improved data transmission signal.